+CC Conall
On 3/9/24 14:06, Jonathan Cameron wrote:
> On Tue, 5 Mar 2024 12:30:53 -0500
> Sean Anderson <sean.anderson@xxxxxxxxx> wrote:
>
>> Hi,
>>
>> When enabling UBSAN on a ZynqMP Ultrascale+, I see the following error during boot:
>>
>> [ 1.447628] ================================================================================
>> [ 1.447832] UBSAN: shift-out-of-bounds in ../drivers/iio/adc/xilinx-ams.c:426:16
>> [ 1.448019] shift exponent 66 is too large for 64-bit type 'long long unsigned int'
>> [ 1.448211] CPU: 2 PID: 1 Comm: swapper/0 Not tainted 6.6.20+ #90
>> [ 1.448368] Hardware name: xlnx,zynqmp (DT)
>> [ 1.448475] Call trace:
>> [ 1.448547] dump_backtrace+0x9c/0x11c
>> [ 1.448655] show_stack+0x18/0x24
>> [ 1.448749] dump_stack_lvl+0xac/0xd4
>> [ 1.448853] dump_stack+0x18/0x24
>> [ 1.448947] ubsan_epilogue+0x10/0x44
>> [ 1.449051] __ubsan_handle_shift_out_of_bounds+0x98/0x134
>> [ 1.449191] ams_enable_channel_sequence+0x22c/0x23c
>> [ 1.449324] ams_probe+0x570/0x6d4
>> [ 1.449423] platform_probe+0x68/0x108
>> [ 1.449530] really_probe+0x158/0x3b0
>> [ 1.449632] __driver_probe_device+0x88/0x1a0
>> [ 1.449747] driver_probe_device+0x3c/0x138
>> [ 1.449859] __driver_attach+0xe4/0x1bc
>> [ 1.449964] bus_for_each_dev+0x78/0xe0
>> [ 1.450068] driver_attach+0x24/0x30
>> [ 1.450167] bus_add_driver+0x110/0x240
>> [ 1.450271] driver_register+0x60/0x128
>> [ 1.450376] __platform_driver_register+0x28/0x34
>> [ 1.450500] ams_driver_init+0x1c/0x28
>> [ 1.450609] do_one_initcall+0x78/0x2c8
>> [ 1.450714] kernel_init_freeable+0x2f8/0x59c
>> [ 1.450831] kernel_init+0x30/0x150
>> [ 1.450932] ret_from_fork+0x10/0x20
>> [ 1.451073] ================================================================================
>>
>> When applying the following patch:
>>
> That channel definition looks suspicious. Anyone shed light on what the channel scan index layout
> is supposed to be?
> There seem to be substantial gaps in used numbers.
> If I read it right the offset to jump over the AUX_CHAN is too large (22 - should be 16) but
> that still ends up with us going above the range of supported scan indexes.
>
> The PL Sequence mask used is GENMASK_ULL(59, 22)
>
> Whilst the bits are set, nothing actually reads them that I can see.
> So why are they set and how are those channels supposed to work?
>
> So agreed buggy; no idea what it supposed to do!
OK, so there are three groups of channels in this device, as set up by
ams_init_module:
- CTRL channels (xlnx,zynqmp-ams)
- PS channels (xlnx,zynqmp-ams-ps)
- PL channels (xlnx,zynqmp-ams-pl)
According to the comment in ams_enable_channel_sequence,
/*
* Enable channel sequence. First 22 bits of scan_mask represent
* PS channels, and next remaining bits represent PL channels.
*/
and indeed, the following code only touches the PS and PL registers. So
I think we just need to add a check for
chan->scan_index >= AMS_CTRL_SEQ_BASE, like in ams_read_raw.
--Sean
>> diff --git a/drivers/iio/adc/xilinx-ams.c b/drivers/iio/adc/xilinx-ams.c
>> index f0b71a1220e0..1ced8cff461a 100644
>> --- a/drivers/iio/adc/xilinx-ams.c
>> +++ b/drivers/iio/adc/xilinx-ams.c
>> @@ -414,8 +414,17 @@ static void ams_enable_channel_sequence(struct iio_dev *indio_dev)
>>
>> /* Run calibration of PS & PL as part of the sequence */
>> scan_mask = BIT(0) | BIT(AMS_PS_SEQ_MAX);
>> - for (i = 0; i < indio_dev->num_channels; i++)
>> + for (i = 0; i < indio_dev->num_channels; i++) {
>> + if (indio_dev->channels[i].scan_index >= 64) {
>> + const struct iio_chan_spec *chan = &indio_dev->channels[i];
>> +
>> + dev_warn(&indio_dev->dev,
>> + "channel %d (%d %d.%d @ %lx) has scan_index %d\n",
>> + i, chan->type, chan->channel, chan->channel2,
>> + chan->address, chan->scan_index);
>> + }
>> scan_mask |= BIT_ULL(indio_dev->channels[i].scan_index);
>> + }
>>
>> if (ams->ps_base) {
>> /* put sysmon in a soft reset to change the sequence */
>>
>> I see these additional outputs:
>>
>> [ 1.447457] iio iio:device0: channel 0 (0 0.0 @ 60) has scan_index 66
>> [ 1.451280] iio iio:device0: channel 1 (0 1.0 @ 6c) has scan_index 67
>> [ 1.451446] iio iio:device0: channel 2 (0 2.0 @ 78) has scan_index 68
>> [ 1.451612] iio iio:device0: channel 3 (0 3.0 @ 7c) has scan_index 69
>> [ 1.451777] iio iio:device0: channel 4 (0 4.0 @ 80) has scan_index 70
>> [ 1.451942] iio iio:device0: channel 5 (0 5.0 @ 84) has scan_index 71
>> [ 1.452107] iio iio:device0: channel 6 (0 6.0 @ 9c) has scan_index 72
>>
>> Indicating that the issue is with the ams_ctrl_channels using the
>> AMS_CTRL_CHAN_VOLTAGE macro.
>>
>> --Sean
>>
>
